Multimode wireless power transmitters and related methods

ABSTRACT

A wireless power transmitter comprises a bridge inverter configured to receive a DC power signal and generate an AC power signal according to an operating frequency, a resonant tank configured to receive the AC power signal and generate an electromagnetic field responsive thereto, and control logic configured to cause the resonant tank to reconfigure and adjust its resonant frequency for a particular receiver type of a wireless power receiver with which a mutual inductance relationship is desired. A method comprises determining a receiver type for a wireless power receiver with which it is desired to establish a mutual inductance relationship for wireless power transfer, and generating a wireless power signal with a wireless power transmitter having an operating frequency and resonant tank that is adjusted for a particular receiver type.

CROSS-REFERENCE TO RELATED APPLICATION

This application is related to U.S. patent application Ser. No. 13/958,389, filed Aug. 2, 2013, and entitled “Multimode Wireless Power Receivers and Related Methods,” the entire disclosure of which is incorporated herein by this reference.

FIELD

Embodiments of the present disclosure relate generally to wireless power transfer and, more particularly, to apparatuses and methods related to a multimode wireless power transmitter.

BACKGROUND

Battery-powered devices (e.g., consumer electronic devices, electric and hybrid automobiles, etc.) are charged from a power source (e.g., AC power outlet) through a charging device. The charging device couples the battery to the power source through an adaptor. The cord extending between the power source and the battery-powered device can take up space. In situations where multiple devices require charging, each with their own charger and cord, the charging area can become cramped and inconvenient.

Approaches are being developed that use over-the-air or wireless power transmission between a transmitter and a receiver coupled to the electronic device. Wireless power transmission using inductive coils is one method considered as an un-tethered method for transferring power wirelessly through a coupled electromagnetic field. In wireless power transmission, power is transferred by transmitting an electromagnetic field through a transmit coil. On the receiver side, a receiver coil may couple with the transmit coil through the electromagnetic field, thus, receiving the transmitted power wirelessly. The distance between the transmitter and receiver coils, at which efficient power transfer can take place, is a function of the transmitted energy and the required efficiency. The coupling coefficient (k) is a function of the distance between the coils, the coil sizes, and materials. The power conversion efficiency (e.g., coupling factor, coupling quality) may be significantly improved if the coils are sized and operated at such a frequency that they are physically within the so-called “near-field zone” of each other.

Wireless power systems are generally intended to operate in a frequency range substantially near (e.g., exactly at) the peak resonance of the resonant tanks of the wireless power devices. Different wireless power devices may be configured differently, which may cause the devices to be incompatible. For example, a wireless power receiver may be designed to operate according to a peak resonance that is substantially different than the peak resonance of a wireless power transmitter. As a result, if one were to attempt to establish wireless power transfer between two dissimilar devices, wireless power transfer parameters such as the system efficiency and the transient response of the wireless power receiver may suffer.

BRIEF SUMMARY

Embodiments of the present disclosure include a wireless power transmitter. The wireless power transmitter comprises a bridge inverter configured to receive a DC power signal and generate an AC power signal according to an operating frequency, a resonant tank configured to receive the AC power signal and generate an electromagnetic field responsive thereto, and control logic configured to cause the resonant tank to reconfigure and adjust its resonant frequency for a particular receiver type of a wireless power receiver with which a mutual inductance relationship is desired.

Another embodiment of the present disclosure includes a wireless power apparatus. The wireless power apparatus comprises a bridge inverter configured to generate an AC power signal responsive to a DC power signal, a resonant tank configured to generate an electromagnetic field having an operating frequency responsive to the AC power signal, and control logic configured to operate a wireless power transmitter as a multimode transmitter. The multimode transmitter has a first mode for wireless power transfer with a first receiver type and a second mode for wireless power transfer with a second receiver type. The resonant tank is configured to exhibit a different resonant frequency for each of the first mode and the second mode.

Another embodiment of the present disclosure includes a method for operating a multimode wireless power transmitter. The method comprises determining a receiver type for a wireless power receiver with which it is desired to establish a mutual inductance relationship for wireless power transfer, and generating a wireless power signal with a wireless power transmitter having an operating frequency and resonant tank that is adjusted for a particular receiver type.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a schematic block diagram of a wireless power transfer system according to an embodiment of the present disclosure.

FIG. 2 is a schematic block diagram of a wireless power transfer system according to an embodiment of the present disclosure.

FIG. 3 is a plot showing the equivalent impedance of a resonant tank as the operating frequency of the wireless power transmitter moves away from the peak resonance of the wireless power receiver.

FIGS. 4-7 are wireless power transmitters according embodiments of the present disclosure.

FIG. 8 is a flowchart illustrating a method for operating a multimode wireless power receiver according to an embodiment of the present disclosure.

DETAILED DESCRIPTION

In the following description, reference is made to the accompanying drawings in which is shown, by way of illustration, specific embodiments of the present disclosure. Other embodiments may be utilized and changes may be made without departing from the scope of the disclosure. The following detailed description is not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims.

Furthermore, specific implementations shown and described are only examples and should not be construed as the only way to implement or partition the present disclosure into functional elements unless specified otherwise herein. It will be readily apparent to one of ordinary skill in the art that the various embodiments of the present disclosure may be practiced by numerous other partitioning solutions.

In the following description, elements, circuits, and functions may be shown in block diagram in order not to obscure the present disclosure in unnecessary detail. Additionally, block definitions and partitioning of logic between various blocks is exemplary of a specific implementation. It will be readily apparent to one of ordinary skill in the art that the present disclosure may be practiced by numerous other partitioning solutions. Those of ordinary skill in the art would understand that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof. Some drawings may illustrate signals as a single signal for clarity of presentation and description. It will be understood by a person of ordinary skill in the art that the signal may represent a bus of signals, wherein the bus may have a variety of bit widths and the present disclosure may be implemented on any number of data signals including a single data signal.

The various illustrative logical blocks, modules, and circuits described in connection with the embodiments disclosed herein may be implemented or performed with a general-purpose processor, a special-purpose processor, a Digital Signal Processor (DSP), an Application-Specific Integrated Circuit (ASIC), a Field-Programmable Gate Array (FPGA) or other programmable logic device, a controller, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A general-purpose processor may be considered a special-purpose processor while the general-purpose processor executes instructions (e.g., software code) stored on a computer-readable medium. A processor may also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

Also, it is noted that the embodiments may be described in terms of a process that may be depicted as a flowchart, a flow diagram, a structure diagram, or a block diagram. Although a process may describe operational acts as a sequential process, many of these acts can be performed in another sequence, in parallel, or substantially concurrently. In addition, the order of the acts may be re-arranged. A process may correspond to a method, a function, a procedure, a subroutine, a subprogram, etc. Furthermore, the methods disclosed herein may be implemented in hardware, software, or both. If implemented in software, the functions may be stored or transmitted as one or more instructions or code on computer readable media. Computer-readable media includes both non-transitory computer storage media and communication media, including any medium that facilitates transfer of a computer program from one place to another.

It should be understood that any reference to an element herein using a designation such as “first,” “second,” and so forth does not limit the quantity or order of those elements, unless such limitation is explicitly stated. Rather, these designations may be used herein as a convenient method of distinguishing between two or more elements or instances of an element. Thus, a reference to first and second elements does not mean that only two elements may be employed or that the first element must precede the second element in some manner. In addition, unless stated otherwise, a set of elements may comprise one or more elements.

Embodiments of the disclosure may include apparatuses, systems, and methods related to a multimode wireless power transmitter. In particular, the multimode wireless power transmitter may be configured to reconfigure a resonant tank of the wireless power transmitter to adjust the resonant frequency of the wireless power transmitter for a receiver type for a wireless power receiver. In addition, the multimode wireless transmitter may adjust the operating frequency for the receiver type.

FIG. 1 is a schematic block diagram of a wireless power transfer system 100 according to an embodiment of the present disclosure. The wireless power transfer system 100 includes a wireless power transmitting apparatus 110, and a wireless power receiving apparatus 120. The wireless power transmitting apparatus 110 includes a wireless power transmitter 112 having a transmit coil 114 configured to generate an electromagnetic field 105 for providing power transfer to the wireless power receiving apparatus 120. The wireless power receiving apparatus 120 includes a wireless power receiver 122 having a receive coil 124 configured to couple with the electromagnetic field 105. The transmit coil 114 and the receive coil 124 may be sized according to the particular devices and applications to be associated therewith. The electromagnetic field 105 may also be referred to as the wireless power signal 105 for power transfer from the wireless power transmitter 112 to the wireless power receiver 122.

An input signal 116 may be provided to the wireless power transmitter 112 for providing the wireless power transmitter 112 with the power for generating the wireless power signal 105 that provides a power transfer to the wireless power receiving apparatus 120. The wireless power receiver 122 may couple to the wireless power signal 105 and generate an output signal 126 in response thereto. The output signal 126 may provide the power that is used by the wireless power receiving apparatus 120 for storing (e.g., charging a battery), consumption (e.g., providing system power), or both.

The wireless power transmitter 112 and the wireless power receiver 122 are separated by a distance (d). In some embodiments, the wireless power transmitter 112 and the wireless power receiver 122 may be configured according to a mutual inductance relationship, such that when the resonant frequency of the wireless power receiver 122 and the resonant frequency of the wireless power transmitter 112 are substantially identical, transmission losses between the wireless power transmitter 112 and the wireless power receiver 122 are minimal. Likewise, the frequency of the wireless power signal 105 may be set by the wireless power transmitter 112 at or near the resonant frequencies of the coils 114, 124. As a result, an efficient power transfer occurs by coupling a large portion of the energy in the near-field of the transmit coil 114 to the receive coil 124 rather than propagating most of the energy in an electromagnetic wave to the far-field. If the wireless power receiving apparatus 120 is in the near-field (within some distance (d)), inductive coupling may occur between the transmit coil 114 and the receive coil 124. The area around the transmit coil 114 and receive coil 124 where this near-field inductive coupling may occur may be referred to as a “coupling region.” Because of this mutual inductance relationship, the wireless power transfer may be referred to as inductive wireless power transfer.

The transmit coil 114 and the receive coil 124 may be configured as a “loop” antenna, which may also be referred to herein as a “magnetic” antenna or an “inductive” antenna. Loop antennas may be configured to include an air core or a physical core such as a ferrite core. Air core loop antennas may be more tolerable to extraneous physical devices placed in the vicinity of the core. Furthermore, an air core loop antenna allows the placement of other components within the core area. In addition, an air core loop may more readily enable placement of the receive coil 124 within a plane of the transmit coil 114 where the coupling region of the transmit coil 114 may be more powerful.

The wireless power transmitting apparatus 110 may include a wireless power transmitter to transmit the wireless power signal 105. The wireless power receiving apparatus 120 may be a mobile electronic device, such as a cell phone, a smart phone, a media player (e.g., mp3 player, DVD player, etc.), an electronic reader, a tablet computer, a personal digital assistant (PDA), a camera, a laptop computer, and personal electronic device in which wireless power signal 105 may be received. The wireless power receiving apparatus 120 may also be a less mobile electronic device, such as a television, personal computer, media player (e.g., DVD player, Blu-ray player, etc.) or any other device that may operate by, and/or store electrical power. The wireless power receiving apparatus 120 may be one of a number of other items, such as an automobile or any other devices that may include batteries that may be charged through the wireless power transmitting apparatus 110.

The wireless power transmitting apparatus 110 may be a device that may, at times, also be the recipient of wireless power transfer. In other words, some devices may be configured as both a wireless power transmitting apparatus 110 and a wireless power receiving apparatus 120, such that the device may transmit wireless power or receive wireless power depending on the mode of operation. Thus, embodiments of the present disclosure include devices that may include a wireless charging transceiver configured to operate in either a transmit mode or a receive mode. Using the term “receiver” indicates that a device is configured to receive wireless power transfer, but should not be interpreted to mean that the device only operates as a receiver. Similarly, using the term “transmitter” indicates that the device is configured to transmit wireless power, but should not be interpreted to mean that the device only operates as a transmitter.

Embodiments of the present disclosure include the wireless power transmitter 112 being configured as a multimode transmitter. The wireless power transmitter 112 may reconfigure its resonant frequency to match a different wireless power receiver type. The wireless power receiver type may be detected identifying at least one distinguishing characteristic of a wireless power receiver that is within a coupling region. For example, there are currently multiple different standards in the wireless power industry. Examples of such standards include the Wireless Power Consortium (WPC) standard, the Power Matters Alliance (PMA) standard, and the Alliance for Wireless Power (A4WP). Each standard may have different characteristics under which they operate. For example, each standard may perform wireless power transfer at different operating frequencies, communicate using different protocols, etc. Reconfiguration of the wireless power transmitter 112 to adjust the resonant frequency thereof may result in the wireless power transmitter 112 being compatible with each of the above standards or any other wireless power standard or transmitter design. The above-listed standards are to be understood as examples of standards with which at least some embodiments of the disclosure may be configured to operate within. Of course, other standards and receiver designs are contemplated.

FIG. 2 is a schematic block diagram of a wireless power transfer system 200 according to an embodiment of the present disclosure. The wireless power transfer system 200 includes a wireless power transmitter 212 having resonant tank 213 that includes a transmit coil 214 coupled with resonant capacitors 215. The wireless power transmitter 212 includes a bridge inverter 217 and control logic 218 coupled with the resonant tank 213. The bridge inverter 217 of the wireless power transmitter 212 may include a full bridge inverter, a half bridge inverter, or other appropriate circuit for receiving a DC input signal 216 and generate an AC signal through the transmit coil 114 for generating the wireless power signal 105. The wireless power receiver 222 includes a resonant tank 223 having a receive coil 224 coupled with resonant capacitors 230. The resonant capacitors 230 are coupled with a rectifier 250. The wireless power transmitter 212 and the wireless power receiver 222 may be incorporated within a wireless power transmitting apparatus 110 (FIG. 1) and a wireless power receiving apparatus 120 (FIG. 1), respectively. The transmit coil 214 and the receive coil 224 (and other components) may be sized according to the particular devices and applications to be associated therewith.

The control logic 218 of the wireless power transmitter 212 may be configured to control one or more operations of the wireless power transmitter 212. Similarly, the control logic 280 of the wireless power receiver 222 may be configured to control one or more operations of the wireless power receiver 222. Each of the control logic 218, 280 may be implemented within a processor (e.g., microcontroller) or other circuitry that is configured (e.g., programmed) to perform various operations of embodiments of the present disclosure. Each of the control logic 218, 280 may further include computer-readable media (e.g., memory) storing computing instructions for execution by the processor related to performing processes of the embodiments of the present disclosure. Memory may include volatile and non-volatile memory.

The wireless power transmitter 212 may be configured to generate a wireless power signal 105 (FIG. 1) responsive to an input signal 216 received by the resonant tank 213. The wireless power receiver 222 may be configured to couple with the wireless power signal 150 (which induces an AC current in the receive coil 224) and generate an output power signal (a DC signal) to provide power to a load 270. As a result, the output power signal may include a rectified voltage (V_(RECT)) and rectified current (I_(RECT)) that is provided to the load 270. The load 270 may include an energy storage device (e.g., battery, such as a lithium-ion battery), system components of a wireless power enabled device, or a combination thereof. Thus, the output signal from the wireless power receiver 222 may be used for charging an energy storage device and/or for providing system power to the various system components of a device.

The wireless power transmitter 212 and wireless power receiver 222 may be generally configured as discussed above with respect to FIG. 1. The configurations of the LC networks within the resonant tanks 213, 223 may generally determine the resonant frequencies of the wireless power transmitter 212 and the wireless power receiver 222, respectively. For example, the resonant frequency of the resonant tanks 213, 223 may be based on the inductance of their respective inductive coil and the capacitance of the plates of the capacitors. The wireless power transmitter 212 and the wireless power receiver 222 may be configured according to a mutual inductance relationship, such that when the resonant frequency of the wireless power receiver 222 and the resonant frequency of the wireless power transmitter 212 are substantially identical, transmission losses between the wireless power transmitter 212 and the wireless power receiver 222 are minimal. As a result, the coupling efficiency and wireless power transfer may be improved. In addition, the frequency of the wireless power signal 105 may be set by the wireless power transmitter 212 at or near the resonant frequencies of the wireless power transmitter 212 and wireless power receiver 222 for minimal transmission losses.

During wireless power transmission, the input signal 216 (a DC signal) may be received by the bridge inverter 217. The bridge inverter 217 may generate an AC current that flows through the resonant tank 213 to generate a time-varying electromagnetic field for transmitting the wireless power signal 105. Thus, the wireless power signal 105 may be a time-varying signal that is substantially sinusoidal, having a frequency that may be based on the switching frequency of the bridge inverter 217 of the wireless power transmitter 212. In some embodiments, the frequency of the wireless power signal 105 may be set according to the desired frequency, such as a frequency for a particular wireless power standard. The resonant tank 213 may be configured such that the resonant frequency is approximately the frequency of the wireless power signal 105. In some embodiments, it may be desirable for the frequency of the wireless power signal 105 to differ somewhat from the resonant frequency of the resonant tank 213, such as to reduce the peak-to-peak current through the transmit coil 214.

In order to receive wireless power signal 105, the wireless power receiver 222 may be placed in the coupling region of the wireless power transmitter 212 such that inductive coupling may be achieved. As a result, the wireless power receiver 222 may receive the wireless power signal 105 and generate an AC power responsive thereto. In order for the power to be used by the load 270, the AC power may be converted to a DC power. The rectifier 250 may generate a rectified voltage (V_(RECT)) as well as a rectified current (I_(RECT)) flowing through the resonant tank 223. In some embodiments, the rectifier 250 may be configured as a synchronous rectifier. As a result, the rectifier 250 may include one or more switches that are controlled in such a manner to generate the DC output power signal (i.e., rectified voltage (V_(RECT)) and rectified current (I_(RECT))). In some embodiments, the rectifier 250 may include one or more diodes configured to generate the DC output power signal.

The wireless power transmitter 212 may be configured to control the bridge inverter 217 to set the switching frequency for a particular receiver type. As a result, the wireless power signal 105 generated by the wireless power transmitter 212 may have a frequency for a particular receiver type. In addition, the control logic 218 may be configured to reconfigure its resonant tank 213 to have a resonant frequency that is appropriate for the frequency of the wireless power signal 105. As an example, the control logic 218 may be configured as a mode controller to control the wireless power transmitter 212 to operate as a multimode transmitter for a different type of receiver. The wireless power transmitter 212 may detect a receiver type by monitoring at least one characteristic of the wireless power receiver 222 with which a mutual inductance relationship is desired. The control logic 218 may be coupled with the resonant tank 213 to monitor signals within the resonant tank 213 to identify distinguishing characteristics of the receiver types. Responsive to the detecting a receiver type, the control logic 218 may control the bridge inverter 217 according to a desired frequency and the resonant tank 213 to configure to have a desired resonant frequency during wireless power transfer.

In addition, each of the control logic 218, 280 may further control other functions of the respective wireless power transmitter 212, wireless power receiver 222, such as controls related to modulation/demodulation, foreign object detection, device operation, etc. The control logic 218, 280 may each include different sub-blocks that perform one or more of the above functions separately rather than by employing within a single process, routine, program, etc. In addition, the control logic 218. 280 may each employ different hardware elements for different functions.

It should be recognized that the devices of a wireless power transfer system 200 may include additional components to perform other features not specifically described herein or shown in the various figures. For example, wireless power enabled devices may include a modulator and/or a demodulator for communicating with other devices, foreign object detection modules, I/O modules for interfacing with a user, memory for storing instructions and data, various sensors, processors, controllers, voltage regulators, among other components. The figures and accompanying description may, therefore, be somewhat simplified to focus on the various apparatuses and methods that are configured to modulate the power generated by the wireless power receiver.

FIG. 3 is a plot 300 showing the equivalent impedance of a resonant tank as the operating frequency of the wireless power transmitter moves away from the peak resonance of the wireless power receiver. In particular, in this example, the peak resonance of the wireless power receiver is about 110 kHz, which is presently the intended operating frequency for the WPC standard. The plot 300 shows that the equivalent impedance of the resonant tank increases as the operating frequency moves away from the peak resonance of the wireless power transmitter. As a result, if a wireless power transmitter having a different operating frequency is desired to enter into a mutual inductance relationship and transfer wireless power, the equivalent impedance of the resonant tank of the wireless power receiver will be relatively higher than if the wireless power transmitter's operating frequency were approximately the peak resonance of the wireless power receiver.

As a further example, if the peak resonance of the wireless power receiver is about 110 kHz (e.g., WPC standard), but the operating frequency of the wireless power transmitter is a different frequency (e.g., between 225 kHz and 278 kHz—present PMA standard), the equivalent impedance of the resonant tank may increase. As a result, the efficiency of the system and the transient response of the rectified voltage (VRECT) may be negatively affected.

Embodiments of the present disclosure, however, include the wireless power transmitter detecting a wireless power receiver type and have the desired operating frequency and reconfiguring the resonant tank to exhibit a different resonant frequency that is closer to the resonant frequency of the wireless power receiver. Detecting the wireless power receiver type may include detecting at least one unique characteristic of the wireless power receiver.

FIG. 4 is a wireless power transmitter 212 according to an embodiment of the present disclosure. As discussed above, the wireless power transmitter 212 may include a bridge inverter 217 operably coupled with a resonant tank 213. The wireless power transmitter 212 may further include control logic 218 that is configured to control the operation of the wireless power transmitter 212 as a multimode transmitter. The control logic 218 may include a receiver type detector 219 that is configured to determine a receiver type and control the reconfiguration of the resonant tank 213 in response thereto.

The bridge inverter 217 may include switches (e.g., S_(F1), S_(F2)) that may be controlled by a switching controller 211. In particular, the switching controller 211 may transmit control signals to alternatingly enable and disable the switches S_(F1), S_(F2) according to a desired operating frequency (i.e., switching frequency). Although a half-bridge inverter is shown in FIG. 4, embodiments may also include a full bridge inverter or other circuit configured to convert a DC input signal 216 to an AC signal. The switching controller 211 may be included within the control logic 218. In some embodiments, the switching controller 211 and the receiver type detector 219 may be implemented as separate components or as part of the same component (e.g., the same controller or IC).

As shown in FIG. 4, the resonant tank 213 may include a transmit coil 214 coupled with resonant capacitors 215. The resonant capacitors 215 include a plurality of capacitors C, C₁, . . . C_(N) coupled with the transmit coil 214. The plurality of capacitors C, C₁, . . . C_(N) are coupled in parallel with each other, and serially with the transmit coil 214. At least some of the capacitors C₁ . . . C_(N) are coupled with a switch S_(c1) . . . S_(CN), respectively. The switches S_(c1) . . . S_(CN) are controlled (e.g., enabled, disabled) by the control logic 218, for example, by the receiver type detector 219. The receiver type detector 219 may generate the control signals that enable the switches S_(C1) . . . S_(CN) to add capacitance to the resonant tank 213 by enabling one or more of the parallel paths that include the capacitors C₁ . . . C_(N) and the switches S_(c1) . . . S_(CN). As a result, the control logic 218 may reconfigure the resonant tank 213 to adjust the resonance of the resonant tank 213 in response to determining the receiver type of the wireless power receiver 222 with which establishing wireless power transfer is desired.

Determining the receiver type may include detecting at least one characteristic of the wireless power transmitter that is unique to a particular receiver type. For example, such characteristics may include the wireless power receiver 222 responding to a unique ping structure, a unique ping sequence, a communication message using a unique protocol, or other distinguishing feature. As to between different wireless standards, such characteristics may be unique to a particular wireless power standard. For example, the receiver type detector 219 may receive an input that assists in the determination of receiver type, and generate the appropriate control signals to the switches S_(C1) . . . S_(C2) to adjust the capacitance of the resonant tank 213. The switches S_(c1) . . . S_(CN) that are enabled depend on the receiver type (particularly its known operating frequency) such that the capacitors C₁ . . . C_(N) that are added result in the resonant tank 213 having a resonant frequency that is closer to the desired operating frequency than it was prior to reconfiguration.

As an example, a wireless power transmitter 212 and a wireless power receiver 222 may be placed within the general vicinity of each other. The wireless power transmitter 212 may detect the presence of the wireless power receiver 222, and transmit a digital ping according to a first communication protocol (e.g., WPC) to the wireless power receiver 222 in order to establish communication and eventually wireless power transfer. The wireless power transmitter 212 may wait for a response from the wireless power receiver 222 for a predetermined period of time before transmitting another digital ping.

As discussed above, different wireless power standards may have different digital ping characteristics. For example, the wireless power receiver 222 may be configured according to one of a first receiver type (e.g., WPC), a second receiver type (e.g., PMA), a third receiver type (e.g., A4WP), and so on. If the wireless power receiver 222 is configured according to a first receiver type that recognizes the digital ping, the wireless power receiver 222 may respond to the ping request. The wireless power transmitter 212 may receive the response from the wireless power receiver 222 and determine that the wireless power receiver 222 is configured according to the first receiver type. As a result, the wireless power transmitter 112 may begin wireless power transfer having the characteristics (e.g., operating frequency and resonant frequency) associated with the first receiver type.

If, however, no response is received by the wireless power transmitter 212 during the predetermined waiting period, the wireless power transmitter 212 may determine that the wireless power receiver 222 is configured according to a different receiver type. As a result, the wireless power transmitter 212 may wait may transmit a digital ping according to a second communication protocol (e.g., PMA). If the wireless power receiver 222 is configured according to a second receiver type that recognizes the second digital ping, the wireless power receiver 222 may respond to the ping request. The wireless power transmitter 212 may receive the response from the wireless power receiver 222 and determine that the wireless power receiver 222 is configured according to the second receiver type. As a result, the wireless power transmitter 112 may begin wireless power transfer having the characteristics (e.g., operating frequency and resonant frequency) associated with the second receiver type. The wireless power transmitter 112 may continue transmitting ping requests associated with different receiver types until a response is received, whereupon the wireless power transmitter 212 begins wireless power transfer according to the characteristics (e.g., operating frequency and resonant frequency) associated with that receiver type. Some transmitter types may send a ping signal that has a constant frequency, while others may have a ping signal that has sweeps across a range of frequencies.

The receiver type detector 219 may receive at least one input from the wireless power transmitter 112 (e.g., at the node before or after the resonant capacitors 215) to detect a unique characteristic of the wireless power receiver 222 (e.g., detecting a response to a particular ping signal).

In some embodiments, the input to the receiver type detector 219 may be manually-driven rather than automatically. For example, the user input may indicate which type of receiver type a particular wireless power receiver 222 is. Non-limiting examples of such a user input includes the user pressing a button, flipping a manual switch, pressing a selection on a touch screen, or other similar input that may be implemented in hardware and/or software.

Once the receiver type is determined, the wireless power transmitter 212 may begin wireless power transfer according to the characteristics of the particular receiver type. For example, the operating frequency and the associated desired resonant frequency for the resonant tank 213 may be determined for the wireless power transmitter 212. The wireless power transmitter 212 may then control the bridge inverter 217 according to the appropriate operating frequency and configure the resonant tank 213 to have a resonant frequency that is associated with that operating frequency, and which more closely matches the operating frequency of the particular wireless power receiver 222 that is desired to engage with for wireless power transfer. Reconfiguration of the resonant tank 213 may include enabling one or more switches S_(C1) . . . S_(CN) that are coupled to the capacitors C₁ . . . C_(N) to adjust the capacitance to the resonant tank 213. In some embodiments the adjusted resonant frequency for the reconfigured resonant tank 213 may be substantially the same as the operating frequency of the wireless power transmitter 212.

In addition to reconfiguring the resonant tank 213, other features of the wireless power transmitter 212 may be reconfigured for a given receiver type. For example, the modulation/demodulation schemes of the wireless power transmitter 212 may be changed to match those of the receiver type.

FIG. 5 is a wireless power transmitter 212 according to another embodiment of the present disclosure. The wireless power transmitter 212 is configured similarly to that of FIG. 4 with the exception that the resonant tank 213 and the control logic 218 are configured such that the inductance of the resonant tank 213 may be adjusted as opposed to the capacitance. In FIG. 5, the resonant tank 213 may include the transmit coil 214 including a plurality of inductors L, L₁, . . . L_(N) coupled in series with the resonant capacitor 215. The plurality of inductors L, L₁, . . . L_(N) may be coupled parallel to each other. At least some of the inductors L₁ . . . L_(N) are coupled with a switch S_(L1) . . . S_(LN), respectively. The switches S_(L1) . . . S_(LN) are controlled (e.g., enabled, disabled) by the control logic 218, for example, by the receiver type detector 219. The receiver type detector 219 generates the control signals that enable the switches S_(L1) . . . S_(LN) to add inductance to the resonant tank 213 by enabling one or more of the parallel paths that include the inductors L₁ . . . L_(N) and the switches S_(L1) . . . S_(LN). As a result, the control logic 218 reconfigures the resonant tank 213 to adjust the resonance of the resonant tank 213 in response to determining a receiver type of the wireless power receiver 222.

FIG. 6 is a wireless power transmitter 212 according to another embodiment of the present disclosure. The wireless power transmitter 212 is configured similarly to that of FIGS. 4 and 5 with the exception that the resonant tank 213 and the control logic 218 are configured such that both the capacitance and the inductance of the resonant tank 213 may be adjusted as opposed to one of them being a fixed value. In FIG. 5, the resonant tank 213 may include the transmit coil 214 including a plurality of inductors L, L₁, . . . L_(N) coupled in series with the resonant capacitor 215, which includes a plurality of capacitors C, C₁, . . . C_(N). The plurality of inductors L, L₁, . . . L_(N) may be coupled parallel to each other. At least some of the inductors L₁ . . . L_(N) are coupled with a switch S_(L1) . . . S_(LN), respectively. The switches S_(L1) . . . S_(LN) are controlled (e.g., enabled, disabled) by the control logic 218, for example, by the receiver type detector 219. The receiver type detector 219 generates the control signals that enable the switches S_(L1) . . . S_(LN) to add inductance to the resonant tank 213.

The plurality of capacitors C, C₁, . . . C_(N) are coupled in parallel with each other. At least some of the capacitors C₁ . . . C_(N) are coupled with a switch S_(C1) . . . S_(CN), respectively. The switches S_(C1) . . . S_(CN) are controlled (e.g., enabled, disabled) by the control logic 218, for example, by the receiver type detector 219. The receiver type detector 219 may generate the control signals that enable the switches S_(C1) . . . S_(CN) to add capacitance to the resonant tank 213 by enabling one or more of the parallel paths that include the capacitors C₁ . . . C_(N) and the switches S_(C1) . . . S_(CN). As a result, the control logic 218 may reconfigure the resonant tank 213 to adjust the resonance of the resonant tank 213 (by adjusting the capacitance, the inductance, or both) in response to determining the receiver type of the wireless power receiver 222 with which establishing wireless power transfer is desired. As a result, the control logic 218 reconfigures the resonant tank 213 to adjust the resonance of the resonant tank 213 in response to determining a receiver type of the wireless power receiver 222.

FIG. 7 is a wireless power transmitter 212 according to another embodiment of the present disclosure. The wireless power transmitter 212 is configured similarly to that of FIG. 6 in that both the capacitance and the inductance of the resonant tank 213 may be adjusted. In FIG. 7, however, the inductors L₁, L₂, . . . L_(N) are coupled in series with a switch path coupled at each node therebetween. At least some of the inductors L₁ . . . L_(N) are coupled with a switch S_(L1) . . . S_(LN), respectively. The switches S_(L1) . . . S_(LN) are controlled (e.g., enabled, disabled) by the control logic 218, for example, by the receiver type detector 219. In some embodiments, the inductors L₁ . . . L_(N) may be discrete inductors having defined nodes therebetween, while some embodiments may include the switches S_(L1) . . . S_(LN) being coupled at tap locations that are intermediate locations between terminals of an individual coil. While this configuration of inductors L₁, L₂, . . . L_(N) is shown in FIG. 7 with an adjustable capacitor network, this configuration of inductors L₁, L₂, . . . L_(N) in series may be coupled with a capacitor network that is fixed in value.

Thus, FIGS. 4-7 describe wireless power transmitters 212 may include resonant tanks 213 having a fixed impedance and an adjustable capacitance (e.g., FIG. 4), an adjustable impedance and a fixed capacitance (e.g., FIG. 5), and both an adjustable impedance and an adjustable capacitance (e.g., FIGS. 6, 7). Although specific configurations of capacitors and inductors are described and shown herein, other configurations are contemplated as being within the scope of disclosure so long as the resonant tank 213 may be reconfigured to adjust the resonant frequency.

FIG. 8 is a flowchart 800 illustrating a method for operating a multimode wireless power transmitter according to an embodiment of the present disclosure. At operation 810, a receiver type for a wireless power receiver may be determined. Determining the receiver type may be responsive to transmitting a digital ping signal from the wireless power transmitter to the wireless power receiver. The digital ping structure may be detected and at least one unique characteristic (e.g., frequency, ping structure, protocol, etc.) may be determined as being associated with a particular receiver type. Such an approach may result in either the wireless power transmitter 212 or the wireless power receiver 222 transmitting a message to the other device using a first encoding scheme and waiting for a response. If no response is receive, a second message may be sent using a second encoding scheme and waiting for a response. Whichever encoding scheme resulted in a response may be used to determine the receiver type. In some embodiments, the receiver type may be a user input (e.g., physical switch, selection in software, etc.) such that the user may indicate which receiver type is desired, and therefore in which mode the wireless power transmitter should be configured to operate.

At operation 820, the resonant frequency of a resonant tank of a wireless power receiver may be adjusted. Adjusting the resonant frequency of the resonant tank may include at least one of adjusting a capacitance of the resonant tank while maintaining a fixed inductance, adjusting an inductance of the resonant tank while maintaining a fixed capacitance, and adjusting both a capacitance an inductance of the resonant tank. Maintaining a fixed inductance and/or capacitance may include hardware that has either a fixed inductance or a fixed capacitance (of course the other of the inductance or capacitance would be adjustable, as in FIGS. 4 and 5). In some embodiments (e.g., FIGS. 6 and 7), both the inductance and capacitance may be adjustable; however, even in such embodiments either a fixed inductance or a fixed capacitance may be maintained simply by adjusting only one of the two even though both may be adjusted. Adjusting the resonant frequency may include reconfiguring the resonant tank during a first mode to have a first resonant frequency associated with a first receiver type, and reconfiguring the resonant tank during a second mode to have a second resonant frequency associated with a second receiver type. In addition to adjusting the resonant frequency of the resonant tank, the wireless power transmitter may operate with an operating frequency that is associated with the resonant frequency and receiver type.

Any number of modes for reconfiguring the resonant tank are contemplated, which may correspond to the number of receiver types recognized by the system. Some transmitters may have more than one mode associated therewith, such that the resonant tank may be configured differently for a particular receiver type depending on other circumstances or factors.

While the present disclosure has been described herein with respect to certain illustrated embodiments, those of ordinary skill in the art will recognize and appreciate that the present invention is not so limited. Rather, many additions, deletions, and modifications to the illustrated and described embodiments may be made without departing from the scope of the disclosure. In addition, features from one embodiment may be combined with features of another embodiment while still being encompassed within the scope of the disclosure as contemplated by the inventor. 

What is claimed is:
 1. A wireless power transmitter, comprising: a bridge inverter configured to receive a DC power signal and generate an AC power signal according to an operating frequency; a resonant tank configured to receive the AC power signal and generate an electromagnetic field responsive thereto; and control logic configured to cause the resonant tank to reconfigure and adjust its resonant frequency for a particular receiver type of a wireless power receiver with which a mutual inductance relationship is desired.
 2. The wireless power transmitter of claim 1, wherein the resonant tank includes a plurality of capacitors that are controllable by at least one switch to adjust capacitance of the resonant tank.
 3. The wireless power transmitter of claim 2, wherein the plurality of capacitors are coupled in parallel with each other, wherein at least one parallel path includes the at least one switch.
 4. The wireless power transmitter of claim 1, wherein the resonant tank includes a plurality of inductors that are controllable by at least one switch to adjust inductance of the resonant tank.
 5. The wireless power transmitter of claim 4, wherein the plurality of inductors are coupled parallel with each other, wherein at least one parallel path includes the at least one switch.
 6. The wireless power transmitter of claim 4, wherein the plurality of inductors are coupled in series with each other, wherein the at least one switch is coupled at a node between inductors and with the rectifier.
 7. The wireless power transmitter of claim 1, wherein the resonant tank includes a plurality of inductors and a plurality of capacitors that are controllable by at least one switch to adjust both capacitance and inductance of the resonant tank.
 8. The wireless power transmitter of claim 1, wherein the determined receiver type is based, at least in part, on a unique characteristic of a wireless power standard.
 9. The wireless power transmitter of claim 8, wherein the unique characteristic includes at least one of a digital ping structure, a communication protocol, and an encoding/decoding scheme.
 10. A wireless power apparatus, comprising: a bridge inverter configured to generate an AC power signal responsive to a DC power signal; a resonant tank configured to generate an electromagnetic field having an operating frequency responsive to the AC power signal; and control logic configured to operate a wireless power transmitter as a multimode transmitter having a first mode for wireless power transfer with a first receiver type and a second mode for wireless power transfer with a second receiver type, wherein the resonant tank is configured to exhibit a different resonant frequency for each of the first mode and the second mode.
 11. The wireless power apparatus of claim 10, wherein the control logic includes a receiver type detector that is configured to determine a receiver type responsive to at least one input, and select a mode associated with the determined receiver type.
 12. The wireless power apparatus of claim 11, wherein the at least one input is an internal signal within the wireless power transmitter.
 13. The wireless power apparatus of claim 12, wherein the internal signal indicates a communication response is received from the wireless power receiver.
 14. The wireless power apparatus of claim 11, wherein the at least one input is a manual user input.
 15. The wireless power apparatus of claim 10, wherein the control logic is configured to control the bridge inverter according to a first operating frequency during the first mode, and according to a second operating frequency during the second mode.
 16. The wireless power apparatus of claim 10, wherein the wireless power apparatus is an electronic device that includes the wireless power transmitter, the wireless power transmitter including the bridge inverter, the resonant tank, and the control logic.
 17. A method for operating a multimode wireless power transmitter, the method comprising: determining a receiver type for a wireless power receiver with which it is desired to establish a mutual inductance relationship for wireless power transfer; and generating a wireless power signal with a wireless power transmitter having an operating frequency and resonant tank that is adjusted for a particular receiver type.
 18. The method of claim 17, wherein generating the wireless power signal includes at least one of: adjusting a capacitance of the resonant tank while maintaining a fixed inductance; adjusting a inductance of the resonant tank while maintaining a fixed capacitance; and adjusting both a capacitance an inductance of the resonant tank.
 19. The method of claim 17, wherein determining the receiver type includes: transmitting a first communication signal from the wireless power transmitter to the wireless power receiver, the first communication signal having a first characteristic associated with a first receiver type; and if no response is received by the wireless power transmitter during a waiting period, reconfiguring the resonant tank and operating frequency and transmitting second communication signal from the wireless power transmitter to the wireless power receiver, the second communication signal having a second characteristic associated with a second receiver type.
 20. The method of claim 19, wherein the first characteristic and the second characteristic differ by at least one of an operating frequency, an encoding/decoding scheme, and ping structure. 